1. Field of the Invention
This invention relates in general to a four-wheel steering apparatus for relatively slow moving vehicles, and more specifically relates to such apparatus that varies, such as riding lawnmowers at certain times, steering of the rear-wheels with respect to the steering of the front-wheels.
2. Description of the Prior Art
To provide vehicles with better maneuverability, it is recognized that four-wheel steering is highly advantageous. A variety of four-wheel steering systems for vehicles are known in the art as disclosed by the following patents: Williamson, U.S. Pat. No. 3,351,147; Andersen, U.S. Pat. No. 3,669,2O2; Dawson, et al, U.S. Pat. No. 4,223,611; Christenson, et al, U.S. Pat. No. 3,198,541; Furukawa, et al, U.S. Pat. No. 4,467,885; Uno, et al, U.S. Pat. No. 4,588,039; Collard, et al, U.S. Pat. No. 4,592,439; and Kanazawa, et al, U.S. Pat. No. 4,621,702.
The above listed patents disclose a variety of four-wheel steering systems for vehicles. For example, in the Kanazawa, et al "702" patent a four-wheel steering system is disclosed that steers the rear wheels in a reverse direction from that of the front wheels at low speeds to enhance the turning capability of the vehicle. Although the system described in the "702" patent appears to be useful in connection with vehicles such as automobiles, such system is not designed to meet the operating conditions of low speed vehicles such as riding lawn mowers.
Four-wheel steering systems present a special problem when used for lawn mowers because of the normally sharply defined boundaries of the areas in which the mowers are operated. For example, when a lawn mower is operated along the side of a house a four-wheel steering system for the front and rear wheels can possibly cause the rear of the lawn mower to swing into the side of the house if the wheels are turned to steer away from the house. This is due to the small turning radius provided by four-wheel steering systems. Such steering would be even more dangerous in the case of a mower operating along side of a steep hill. In such instance, the rear of the mower may actually be swung over the side of the hill.
The present invention provides a four-wheel steering system for a vehicle, preferably such as a lawn mower, that has a control system for delaying, at certain instances, steering of the back wheels with respect to the steering of the front wheels.